Semiconductor Device and Method of Manufacturing Same

ABSTRACT

A FET is formed on a semiconductor substrate, a curved surface having a radius of curvature is formed on an upper end of an insulation, a portion of a first electrode is exposed corresponding to the curved surface to form an inclined surface, and a region defining a luminescent region is subjected to etching to expose the first electrode. Luminescence emitted from an organic chemical compound layer is reflected by the inclined surface of the first electrode to increase a total quantity of luminescence taken out in a certain direction.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device having a circuitcomposed of field effect transistors (referred below to as FET), and amethod of manufacturing the same. In addition, FET referred to in thespecification of the present application indicates general elements, inwhich the basic principle of FET is embodied as an element, and includesMIS FET, MOS FET making use of oxides for insulator films, and thin filmtransistors making use of semiconductor thin films. The inventionspecifically relates to an electronic equipment, on which asemiconductor device having a Light Emitting Diode is loaded as a part.

In addition, a semiconductor device referred to in the specification ofthe present application indicates devices in general making use ofsemiconductor characteristics to be able to function, and electro-opticdevices, light emitting devices, semiconductor circuits, and electronicequipments are all indicated as semiconductor devices.

Also, semiconductor devices include all modules, in which connectors,for example, FPC (Flexible printed circuit), or TAB (Tape AutomatedBonding) tape, or TCP (Tape Carrier Package), are mounted on a lightemitting device, modules, in which a printed circuit board is providedon a tip end of TAB tape, or TCP, or modules, in which an IC (integratedcircuit) is packaged directly on a light emitting diode by means of COG(Chip On Glass).

In recent years, light emitting devices having an EL element as aself-light emitting element have been actively studied, and inparticular, attention has been paid to light emitting devices making useof organic materials as an EL material. Such a light emitting device iscalled an EL Display, or a Light Emitting Diode. Note that, a lightemitting device referred to in the specification of the presentapplication indicates an graphic display device, light emitting device,or a light source (includes a lighting device).

In addition, EL elements comprise a layer (referred below to as ELlayer) containing an organic chemical compound, in which light emitting(Electro Luminescence) generated upon application of an electric fieldis obtained, anode, and cathode. While light emitting in organicchemical compounds includes emission (fluorescence) generated whenreturned to a ground state from a singlet excitation state, and emission(phosphorescence) generated when returned to a ground state from atriplet excitation state, light emitting devices fabricated by adeposition apparatus and a deposition method, according to theinvention, are applicable to the cases where either emission is used.

light emitting devices has a feature in that there is caused no problemin angle of visibility because they are of self-light emitting typeunlike liquid crystal displays. That is, the devices are more suitablethan liquid crystal displays when used as displays in the open air, anduse thereof has been proposed in various configurations.

While an EL element is configured such that an EL layer is interposedbetween a pair of electrodes, the EL layer generally has a laminatedstructure. Typically, a laminated structure “hole transport layer/lightemitting layer/electron transport layer” is listed. This structure isvery high in light emitting efficiency and adopted by almost all lightemitting devices, which are presently being studied and developed.

Also, light emitting elements formed by a cathode, an EL layer, and ananode are called EL elements, and include two types, that is, a system(simple matrix system), in which an EL layer is formed between two kindsof stripe-shaped electrodes provided perpendicular to each other, and asystem (active matrix, system), in which an EL layer is formed between apixel electrode connected to TFT and arranged in a matrix configurationand an opposed electrode. However, it is believed that in the case wherepixels are increased in density, the active matrix system, in whichswitches are provided every pixel (or one dot), is advantageous.

Also, active matrix type light emitting devices have been structured, inwhich an electrode electrically connected to a TFT on a substrate isformed as an anode, an organic compound layer is formed on the anode, alight emitting element with a cathode formed on the organic compoundlayer is provided, and light generated on the organic compound layer istaken out toward a TFT from the anode being a transparent electrode.

Hereupon, according to the invention, active matrix type light emittingdevices are fabricated having a light emitting element of a structure(referred below to as upper-surface outgoing structure), in which afirst electrode is formed as an anode, a layer containing an organiccompound layer is formed on the anode, and a cathode composed of asecond electrode for transmission of emission is formed on the layercontaining an organic compound layer. Alternatively, active matrix typelight emitting devises are fabricated having a light emitting element ofa structure, in which a first electrode is foamed as a cathode, a layercontaining an organic compound layer is formed on the cathode, and ananode composed of a second electrode for transmission of emission isformed on the layer containing an organic compound layer.

Also, all the light generated on the layer containing an organiccompound layer is not taken out toward an observer (user) but light isemitted, for example, laterally (direction in parallel to the substratesurface), and as a result, the light emitted laterally is not taken outand so constitutes a loss. Hereupon, the invention has its object toprovide a light emitting device structured to increase a quantity oflight taken out in a certain direction, and a method of fabricating thesame.

Also, in a light emitting element having an organic compound, letconsider a path, along which electrons and holes injected fromelectrodes are converted into photons to be finally taken out of theelement. Only a certain ratio of electric current flowing through anexternal circuit can contribute to carrier combination as anelectron-hole pair, and a portion of the electron-hole pair asrecombined is consumed for generation of light emitting molecularexcitons. The generated excitons are converted into photons in a ratioprescribed by fluorescence quantum efficiency, and the remainder isdeactivated in various paths to make, for example, thermal deactivationand emission of infrared light. Accordingly, when such light emittingelement is driven to make emission, Joule heat is generated to incurdecomposition and crystallization of an organic compound layer, thuscausing deterioration of the light emitting element.

SUMMARY OF THE INVENTION

Hereupon, the invention has its object to efficiently remove or reducegeneration of heat in a light emitting element having an organiccompound layer.

The invention comprises using a semiconductor substrate to form a FET,forming a first electrode, which constitutes an electrode (drainelectrode or source electrode) of the FET and is made of a laminated ofmetallic layers, forming an insulation (called bank, partition) coveringan end of the first electrode, thereafter performing etching of aportion of the insulation in self-alignment with the insulation as amask and performing etching of a central portion of the first electrodeto thin the area and to form a stepped portion on the end. Such etchingthins the central portion of the first electrode into a flat surface,and that end of the first electrode, which is covered by the insulation,is made thick in shape, that is, concave-shaped (depression). And alayer containing an organic compound and a second electrode are formedon the first electrode to complete a light emitting element.

According to the invention, an inclined surface formed on astepped'portion of the first electrode reflects or collects lateralemission to increase a quantity of light taken out in a certaindirection (direction passing through the second electrode).

Accordingly, a portion defining the inclined surface is preferably madeof a light reflective metal, for example, a material having as a maincomponent aluminum, silver, or the like, and the central portion incontact with the layer containing an organic compound is preferably madeof an anode material having a large work function, or a cathode materialhaving a small work function.

Also, the invention uses a semiconductor substrate of excellent heatdissipation . to be able to efficiently remove or reduce generation ofheat. Also, it is possible to form on the semiconductor substrate of theinvention various circuits (drive circuit having CMOS circuit, such asan inverter circuit, NAND circuit, AND circuit, NOR circuit, OR circuit,shift register circuit, sampling circuit, D/A converter circuit, A/Dconverter circuit, buffer circuit, or the like, correction circuit,memory element such as CPU, SRAM, DRAM, or the like, photoelectrictransducer composed of PIN connection of silicone, thin-film diode,resistive element, or the like) other than a light emitting element anda FET connected to the light emitting element at a time. In addition, itis also possible to fabricate minute patters, and besides tothree-dimensionally integrate these circuits. Accordingly, it ispossible to decrease an area occupied by various circuits and a drivecircuit having an element, so that since an area of a frame part is madesmall, a whole size can be made compact further.

Also, while in the above configuration, the first electrode and thedrain electrode of a FET are made unitary to reduce the total number ofmasks and processes, one photomask may be added to make the firstelectrode from a different material. Also, in order to provide for anincrease in numerical aperture, two photomasks may be added to form afirst electrode composed of laminated metallic layers connected to adrain electrode (or a source electrode) of a FET through an insulatingfilm.

A constitution of the invention disclosed in the specification of thepresent application provides a semiconductor device comprising a lightemitting element comprising a first electrode connected to a fieldeffect transistor provided on a semiconductor substrate, an insulationcovering an end of the first electrode, a layer containing an organicchemical compound and contacting with the first electrode, and a secondelectrode contacting with the layer, and wherein the first electrode hason an end thereof an inclined surface directed toward a center of thefirst electrode, and the inclined surface reflects light emitted fromthe layer containing an organic chemical compound.

Also, a further constitution of the invention provides a semiconductordevice comprising a light emitting element comprising a first electrodeconnected to a field effect transistor provided on a semiconductorsubstrate, an insulation covering an end of the first electrode, a layercontaining an organic chemical compound and contacting with the firstelectrode, and a second electrode contacting with the layer, and whereina center of the first electrode is concave-shaped to have a smaller filmthickness than that of the end thereof.

Also, a still further constitution of the invention provides asemiconductor device comprising a light emitting element comprising afirst electrode connected to a field effect transistor provided on asemiconductor substrate, an insulation covering an end of the firstelectrode, a layer containing an organic chemical compound andcontacting with the first electrode, and a second electrode contactingwith the layer, and wherein the first electrode is of multi-layeredstructure and the number of lamination at a center of the firstelectrode is greater than that at an end thereof.

Also, the invention contrives a configuration of insulations (calledbank, partition, barrier, or the like) provided between respectivepixels in order to eliminate failure in coverage when an organicchemical compound layer composed of a high polymer is fowled by means ofa coating method. The respective configurations has a feature in thatupper ends of the insulations have a curved surface, of which a radiusof curvature is 0.2 μm to 3 μm. Also, the taper angle of the insulationssuffices to be 35° to 55°.

The radius of curvature is provided to make favorable a covering qualityfor the stepped portion, so that deposition can be made even when alayer formed later and containing an organic chemical compound is verythin.

Also, in the respective constitutions, the first electrode comprises aninclined surface directed toward a center thereof and an inclination(also called taper angle) is more than 30° but less than 70°. Inaddition, it is necessary to appropriately set an inclination, materialand film thickness of the organic chemical compound layer, or a materialand film thickness of the second electrode so that light reflected bythe inclined surface of the first electrode is prevented from beingdispersed between the layers and becoming stray light.

Also, in the respective constitutions, the second electrode comprises aconductive film, for example, a thin metallic film, transparentconductive film, or a film of a lamination thereof, permittingpermeation of light.

Also, in the respective constitutions, the first electrode isconcave-shaped and formed in self-alignment with the insulation as amask. Accordingly, no mask is added in forming a shape of the firstelectrode. In addition, a stepped portion (upper end of the inclinedportion) of the first electrode corresponds substantially to the side ofthe insulation, and it is desired that an inclination of the inclinedsurface of the first electrode and an inclination of the side of theinsulation are preferably equal to each other in view of covering thestepped portion.

Also, in the respective constitutions, the first electrode is a part ofa drain electrode or a source electrode of the field effect transistor.By making a part of a drain electrode or a source electrode the firstelectrode, simultaneous formation is made possible and so it is possibleto reduce the number of masks and processings. Alternatively, the firstelectrode and a drain electrode or a source electrode of the fieldeffect transistor may be formed separately in differed processings, inwhich case the first electrode can be made of a different material fromthat of a drain electrode or a source electrode of the field effecttransistor.

Also, in the respective constitutions, the first electrode is an anodeand the second electrode is a cathode. Alternatively, the firstelectrode is a cathode and the second electrode is an anode.

Also, in the respective constitutions, the layer containing an organicchemical compound is made of a white light emitting material, andcombines with a color filter provided on a sealing agent, andalternatively, the layer containing an organic chemical compound is madeof a monochromatic light emitting material, and combines with a colorconversion layer or a color layer provided on a sealing agent.

Further, according to the invention, reduction in membrane resistance ofan electrode (electrode, which light permeates) being a cathode may beachieved by using the deposition method making use of a deposition maskto form wirings (called auxiliary wirings, or a third electrode) on theinsulation arranged between respective pixels after formation of astepped portion of the first electrode. Also, the invention has afeature in that wirings taken out are formed by the use of the auxiliarywirings to be connected to other wirings present in lower layers.

Also, in the respective constitutions, the field effect transistor is aMISFET, MOSFET, or a TFT.

Also, in the respective constitutions, a CPU, memory element, thin filmdiode, photoelectric transducer, or a resistive element is provided onthe semiconductor substrate.

Also, a constitution of the invention for materializing the respectiveconstitutions provides a method of fabricating a semiconductor devicehaving a light emitting element comprising an anode, a layer containingan organic chemical compound and contacting with the anode, and acathode contacting with the layer containing an organic chemicalcompound, comprising the steps of forming a field effect transistor on asemiconductor substrate; forming an insulation, which covers an end of afirst electrode being a part of a drain electrode or a source electrodeof the field effect transistor; performing etching with the insulationas a mask to thin a center of the first electrode so that an inclinedsurface is exposed along an edge of the first electrode, which comprisesa lamination of metallic layers; forming a layer containing an organicchemical compound and contacting with the center and the inclinedsurface of the first electrode; and forming a second electrode, which ismade of a metallic thin film permitting permeation of light, on thelayer containing an organic chemical compound.

Also, in the constitution relating to the fabricating method, the firstelectrode comprises a lamination of a light-reflective metallic layerand a metallic layer serving as a stopper for etching, thelight-reflective metallic layer is subjected to etching, and alight-reflective metallic material is exposed to the inclined surface.

Also, by subjecting the first electrode to etching, surfaces of themetallic layer serving as a stopper for etching may be somewhatsubjected to etching.

Also, in the constitution relating to the fabricating method, the firstelectrode is an anode and made of a metallic layer having a greater workfunction than that of the second electrode.

Also, in the constitution relating to the fabricating method, the firstelectrode comprises a lamination of a first metallic layer containingtitanium, second metallic layer containing titanium nitride or tungstennitride, third metallic layer containing aluminum, and a fourth metalliclayer containing titanium nitride.

In addition, since the first metallic layer contacts with a sourceregion and a drain region of a it suffices to select a metallic material(typically, titanium), which is favorable in ohmic contact withsilicone, a material having a large work function is preferable for asecond metallic layer functioning as an anode, a metallic materialhaving a high light reflectance is preferable for a third metallic layerreflecting light from a light emitting element, and a metallic material(titanium nitride, titanium) for preventing hillock and whisker of thethird metallic layer and preventing mirror reflection on the thirdmetallic layer is preferable for a fourth metallic layer.

Also, the first electrode is not limited to the four-layered structurebut is not specifically limitative provided that the electrode comprisesat least two layers composed of a metallic layer functioning as anodeand a metallic layer having an inclined surface, which reflects lightfrom a light emitting element.

Also, FIG. 12 indicates reflectance of an aluminum film containing avery small amount of Ti and reflectance of a TiN film (100 nm). Titaniumnitride is a material capable of preventing mirror reflection. Also,when titanium nitride is used for anode, it makes little reflection, sothat interference due to a return light of a light emitting element isnot generated. Accordingly, even when any circularly polarized plate isnot provided, a panel structure can be made.

For example, the first electrode may be of a six-layered structurecomposed of titanium as a first metallic layer, titanium nitride as asecond metallic layer, a metallic layer containing aluminum as a thirdmetallic layer, titanium nitride as a fourth metallic layer, a metalliclayer containing aluminum as a fifth metallic layer, and titaniumnitride as a sixth metallic layer. The six-layered structure makes thefourth metallic layer an anode and has an inclined surface of the fifthmetallic layer reflecting light of a light emitting element, and themetallic layer containing aluminum is provided below an anode, so thatreduction in resistance can be achieved in the whole first electrode.

Also, in the constitution relating to the fabricating method, a metalliclayer being an anode may be increased in work function by performing anultraviolet irradiation processing (called UV ozonization) in ozoneatmosphere. FIG. 13 shows results of measurement of changes in workfunction with UV ozonization time. As shown FIG. 13, titanium nitridehas a work function of 4.7 eV, and the work function can be made 5.05 eVby means of UV ozonization (six minutes). In addition, a tendency, inwhich a work function is increased, is obtained for tantalum nitride inthe same manner. Also, in the constitution relating to the fabricatingmethod, a metallic layer being an anode may be increased in workfunction by performing a plasma processing using one or several onesof-gases such as N₂, O₂, Ar, BCl, and Cl₂.

Incidentally, measurement of work function shown in FIG. 13 is performedin the atmosphere and using “photoelectron spectroscopy apparatus AC-2”manufactured by Riken Keiki Company with photoelectron spectroscopy.

Also, in the case where etching is performed with the insulation as amask and plasma etching is used in a processing, in which a center ofthe first electrode is thinned so as to expose the inclined surfacealong an edge of the first electrode, a metallic layer being an anodecan be increased in work function depending upon an etching gassimultaneously with thinning of the center.

Also, in the constitution relating to the fabricating method, theinsulation covering the end of the first electrode has a curved surfacehaving a radius of curvature to at an upper end thereof and the radiusof curvature is 0.2 μm to 0.3 μm.

Also, in the constitution relating to the fabricating method, the fieldeffect transistor is a MISFET, MOSFET, or a TFT.

In addition, EL elements comprise a layer (referred below to as ELlayer) containing an organic chemical compound, in which light emitting(Electro Luminescence) generated upon application of an electric fieldis obtained, anode, and cathode. While light emitting in organicchemical compounds includes emission (fluorescence) when returned to aground state from a singlet excitation state, and emission(phosphorescence) when returned to a ground state from a tripletexcitation state, light emitting devices fabricated by a manufacturingapparatus and a deposition method, according to the invention, areapplicable to the cases where either emission is used.

While a light emitting element (EL element) having an EL layer isconfigured such that the EL layer is interposed between a pair ofelectrodes, the EL layer ordinarily has a laminated structure.Typically, a laminated structure “hole transport layer/light emittinglayer/electron transport layer” proposed by Tang of Kodak EastmanCompany is listed. This structure is very high in light emittingefficiency and adopted by almost all light emitting devices, which arepresently being studied and developed.

Also, a hole injection layer/hole transport layer/ light emittinglayer/electron transport layer or a hole injection layer/hole transportlayer/ light emitting layer/electron transport layer/hole injectionlayer may be laminated in this order on an anode. A fluorescent pigmentor the like may be doped on a light emitting layer. Also, all theselayers may be formed from a low molecular material, or a high polymermaterial. In addition, all layers provided between a cathode and ananode are referred generally to EL layers. Accordingly, all the holeinjection layer, the hole transport layer, the light emitting layer, theelectron transport layer and the hole injection layer are included in ELlayers.

Also, with the light emitting device of the invention, a driving methodin screen display is not specifically limitative but may adopt, forexample, dot sequential driving method, line sequential driving method,surface sequential driving method and so on. Typically, it suffices thatthe line sequential driving method be adopted, and a time sharinggradation driving method and a area gradation driving method beappropriately used. Also, an image signal being input into a sourcewiring of the light emitting device may be an analog signal or a digitalsignal, and it suffices that a driving circuit be appropriately designedin conformity with an image signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views showing a first embodiment;

FIGS. 2A and 2B are views showing an example 1;

FIGS. 3A to 3C are views showing an example 1;

FIG. 4 is a view showing a third embodiment;

FIGS. 5A to 5C are views showing a second embodiment;

FIGS. 6A and 6B are views showing an example 2;

FIG. 7 is a view showing an example 2;

FIG. 8 is a system block diagram of a semiconductor device comprising alight emitting device;

FIGS. 9A and 9B are views showing an example 3;

FIGS. 10A to 10F are views showing example of electronic equipments;

FIGS. 11A and 11B are views showing example of electronic equipments;

FIG. 12 is a graph indicating reflectance of an aluminum film containinga very small amount of Ti and reflectance of a TiN film (100 nm); and

FIG. 13 is a graph indicating changes in work function with UVozonization time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the invention will be described below.

First Embodiment

FIG. 1A is a cross sectional view showing an active matrix type lightemitting device (a portion of a pixel). Here, an explanation will beexemplarily given to a light emitting element, in which a layercontaining an organic compound composed of a white light emittingpolymeric material.

In FIG. 1A, a FET (PMOSFET) provided on a semiconductor substrate 10 isan element for controlling an electric current flowing to a white lightemitting layer 20, the reference numerals 13, 14 denoting source regionsor drain regions.

A N-type or P-type single crystal silicon substrate ((100) substrate,(110) substrate, (111) substrate, or the like), or a high puritysemiconductor substrate can be used for a semiconductor substrate 10.Also, for example, a wafer (circular) having a diameter of 200 mm to 300mm is cut to make a rectangular substrate, and then a FET is formedthereon. Alternatively, multiple patterning may be performed, in whichthe wafer is divided into sections of a desired size after a FET and alight emitting element are formed. Also, a chemical compoundsemiconductor substrate typified by a GaAs substrate, InP substrate, GaNsubstrate for GaN system epitaxis, SiC substrate, sapphire substrate,ZnSe, or the like may be used for the semiconductor substrate 10. Also,a SOI (Si on Insulator) substrate structure may be formed by means ofthe wafer applying method and the SIMOX (separation by implanted oxygen)method.

A field oxide film 11 is formed on the semiconductor substrate 10, and agate insulating film 12 is provided below a gate electrode 15. While anexample, in which a side wall is formed laterally of the gate electrode15, it is not limitative. The field oxide film 11 is formed on anopening by using the selective oxidation method (also called LOCOSmethod) for separation of respective elements to perform thermaloxidation of the semiconductor substrate to form an oxide film (padoxide film), using the CVD method to deposit a mask nitride film on theoxide film, performing patterning, exposing a silicone surface only tothe opening to perform thermal oxidation.

Also, trench separation, in which design rule is suited to fineprocessing of at most 0.25 μm, may be used in place of the LOCOS method.The trench separation is a method of performing element separation byrefilling an insulating material such as oxide film, or the like, intogrooves after the grooves (trenches) are formed on a silicone substrate.

Also, the reference numeral 16 a denotes an interlayer insulating filmcomposed to of a silicon nitride film and a silicon nitride and oxidefilm, and the reference numeral 16 b denotes a flattened insulating filmcomposed of a photosensitive or non-photosensitive organic material(polyimide, acrylic, polyimide, polyimideamide, resist, orbenzocyclobutene) formed by the coating method, or a flattenedinsulating film (containing a coated silicon oxide film, PSG (phosphorusadding glass, BPSG (boron and phosphorus adding glass), or the like)composed of an inorganic material, or a laminated film thereof. Also,although not shown, a single FET (NMOS or PMOS) or a plurality of FETsare provided on a single pixel. In the case where NMOS and PMOS areformed on the same semiconductor substrate, there is a need of providinga region (well) having a different conductivity from that of thesubstrate, methods therefor including the P well system, in which a Pwell is formed on a N type substrate, a N channel transistor is formedon the P well, and a P channel transistor is formed on the N typesubstrate, the N well system, in which a N well is formed on a P typesubstrate, a P channel transistor is formed on the N well, and a Nchannel transistor is formed on the P type substrate, and the twin wellsystem, in which a N well and a P well are formed on a N type or P typesubstrate, a P channel transistor is formed on the N well, and a Nchannel transistor is formed on the P well. Also, while there is shown aFET having one channel forming region, this is not limitative, and a FETmay have a plurality of channels.

Also, the reference numerals 18 a to 18 d denote a first electrode, thatis, an anode (or cathode) of a light emitting element, and 21 denotes asecond electrode, that is, a cathode (or an anode) of the light emittingelement. Here, a titanium film 18 a, titanium nitride film 18 b, film 18c containing aluminum as a main component, and a titanium nitride film18 d are laminated in this order, and the film 18 b contacting with alayer 20 containing an organic compound functions as an anode. Also, apower supply line 17 is formed in the same laminated structure. Thelaminated structure contains the film containing aluminum as a maincomponent and can be made a wiring of low resistance, and a sourcewiring 22 and the like are formed at the same time.

Also, in order to provide for white light emitting, after a poly(ethylenedioxythiophene)/poly (styrenesulfonic acid) aqueous solution(PEDOT/PSS) acting as a hole injection layer is applied on a wholesurface to be baked, a polyvinyl carbazole (PVK)solution doped with alight emitting center pigment (1,1,4,4-tetraphenyl-1,3-butadiene (TPS),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-bilane(DCM1),Nile red, coumarin 6, or the like) acting as a light emitting layer isapplied as the layer 20, containing an organic compound, on a wholesurface to be baked. In addition, the PEDOT/PSS uses water as a solventand is not dissolved in an organic solvent. Accordingly, when the PVK isapplied thereon, there is no fear of redissolution. Also, since thePEDOT/PSS and the PVK are different in solvent from each other, it ispreferable that the same deposition chamber is not used. Also, the layer20 containing an organic compound can be made a monolayer, and a1,3,4-oxadiazole derivative (PBD) of electron transport property may bedispersed in polyvinyl carbazole (PVK) of hole transport property. Also,white light emitting can be obtained by dispersing a 30 wt % PBD as anelectron transport agent and dispersing suitable amounts of pigments offour kinds (TPD, coumarin 6, DCM1, Nile red).

Also, white light emitting can be obtained as a whole by appropriatelyselecting a film containing a red light emitting organic compound, filmcontaining a green light emitting organic compound, and a filmcontaining a blue light emitting organic compound, and overlapping themfor color mixture.

Also, after the deposition method is used to form CaF₂ having a filmthickness of 1 nm to 10 nm, the sputtering method or deposition methodis used to finally form an Al film having a film thickness of about 10nm to have an electrode 21 functioning as a cathode. For the cathode, itis necessary to appropriately select a film thickness and a material topermit passage of light from the layer 20 containing an organiccompound. In addition, a cathode referred to in the specification of thepresent application is s defined to indicate not only a monolayer madeof a material having a small work function but also a laminated filmcomposed of a thin film made of a material having a small work functionand a conductive film.

When an Al film is used as the second electrode 21, a materialcontacting with the layer 20 containing an organic compound can be madeof one other than an oxide, 10 and so the light emitting device can beimproved in reliability. In addition, a transparent conductive film (ITO(indium oxide stannic oxide alloy), indium oxide zinc oxide (In₂O₃—ZnO),zinc oxide (ZnO), or the like) may be used for the second electrode 21in place of an Al film. Also, CaF₂ may be replaced by a thin metalliclayer (typically, an alloy such as MgAg, MgIn, AlLi, or the like).

Also, both ends of the first electrode and a portion therebetween arecovered with an insulation 19 (called barrier or bank). In theinvention, a cross sectional shape of the insulation 19 is essential.Etching processing for formation of the insulation 19. forms a concaveshape of the first electrode 18. In the case where no curved surface isprovided on an upper end of the insulation 19, failure in deposition, inwhich a projection is formed on the upper end of the insulation 19,becomes liable to be generated. Hereupon, according to the invention, acurved surface having a radius of curvature is formed on the upper endof the insulation 19, a part of the first electrode 18 c, 18 d isexposed corresponding to the curved surface to form an inclined surface,and the etching processing is carried out so as to cause the firstelectrode 18 b to be exposed to a region making a light emitting region.Also, a processing (CMP processing, or the like) for flattening asurface of the exposed first electrode 18 b may be carried out. Also,the etching processing may be carried out so as to increase a filmthickness of the first electrode 18 b and to make a part of the firstelectrode 18 b an inclined surface. In addition, the radius of curvatureis preferably 0.2 μm to 0.3 μm. According to the invention, coverage forthe organic compound film and the metallic film can be made favorable.Also, both a taper angle at the side of the insulation 19 and a taperangle at the inclined surface of the first electrode 18 c, 18 d sufficeto be 45°±10°.

In addition, the processing for performing etching for the concave shapeof the first electrode is not specifically limitative, and dry etching,or wet etching, or an etching method composed of a combination thereofmay be adopted. The film can be etched into a desired tapered shape byusing, for example, the ICP (Inductively Coupled Plasma) etching methodand appropriately adjusting the etching conditions (electric energyapplied to the coil type electrode, electric energy applied to theelectrode on a substrate side, temperature of the electrode on thesubstrate side, or the like). In addition, a chlorinated gas typified byCl₂, BCl₃, SiCl₄, CCl₄, or the like, or a fluorochemical gas typified byCH₄, SF₆, NF₃, or the like, or O₂ can be used appropriately. Here, RF(13.56 MHz) electric power of 450 W is made on the coil type electrodeat pressure of 1.9 Pa, RF (13.56 MHz) electric power of 100 W is alsomade on the substrate (specimen stage) side, and a substantiallynegative self-bias voltage is applied. In addition, the electrode on thesubstrate side is sized to have an area of 12.5 cm×12.5 cm, and the coiltype electrode (here, quartz disk provided with a coil) is a disk sizedto have an area of 25 cm in diameter. The shape of the first electrodeand the insulation can be formed by using BCl₃ and Cl₂ for the etchinggas and making flow ratios of the respective gases 60/20 (sccm).

Also, a three-layers structure suffices, for example, a titanium film 18a, titanium nitride film 18 b, and a film 18 c containing aluminum as amain component may be laminated in this order.

The invention has a feature in that a light emitting from the organiccompound layer 20 is reflected by the inclined surface of the firstelectrode 18 c, 18 d to increase a total quantity of light taken out ina direction indicated by the arrows in FIG. 1A.

Also, as shown in FIG. 1B, a auxiliary electrode 23 may be provided onthe conductive film 21 in order to attain a low resistance in theconductive film (cathode) 21. The auxiliary electrode 23 suffices to beselectively formed by the deposition method, in which a deposition maskis used.

Also, although not shown, it is preferable to form a protective film onthe second electrode 21 in order to enhance reliability in the lightemitting device. The protective film is a thin film having as its maincomponent an insulating film, which has, as its main component, siliconnitride and silicon nitride and oxide obtained by the sputtering method(DC system, RF system), or a thin film having as its main componentcarbon. A silicon nitride film is obtained by the use of a silicontarget and formation in an atmosphere containing nitrogen and argon.Also, a silicon nitride target may be used. Also, the protective filmmay be formed by the use of a deposition device, in which remote plasmais used. Also, in order to have a light emitting passing through theprotective film, it is preferable that a film thickness of theprotective film be as thin as possible.

The invention has a feature in that the thin film having as its maincomponent carbon is a DLC (Diamond like Carbon) having a film thicknessof 3 to 50 nm. The DLC film has a SP³ coupling as a coupling betweencarbon in short-distance order but an amorphous structuremacroscopically. The DLC film has a composition of carbon of 70 to 95atom % and hydrogen of 5 to 30 atom %, the film being very hard andexcellent in insulating property. Also, such DLC film has a feature inthat gas permeability for water vapor, oxygen, or the like is low. Also,it has been known that such film has the hardness of 15 to 25 GPa inmeasurement with a micro hardness meter.

The DLC film can be formed by the use of the plasma CVD method(typically, the RF plasma CVD method, the microwave CVD method, theelectron cyclotron resonance (ECR) CVD method, or the like), thesputtering method, or the like. Whichever deposition method is used, itis possible to form a DLC film with good adhesion. Deposition of the DLCfilm is made while mounting a substrate on a cathode. Alternatively, aminute and hard film can be formed by application of a negative bias andutilization of ion bombardment to some extent.

Deposition is carried out by using hydrogen gas and hydrocarbon gas (forexample, CH₄, C₂H₂, C₆H₆, or the like) as a reactant gas for use indeposition, causing ionization with glow discharge, and accelerating andcausing ions to strike against a cathode, on which negative self-bias isapplied. Thus it is possible to obtain a minute and hard DLC film. Inaddition, the DLC film is an insulating film being transparent ortranslucent for visible light.

In the specification of the present application, being transparent forvisible light indicates that transmissivity for visible light is 80 to100%, and being translucent for visible light indicates thattransmissivity for visible light is 50 to 80%.

Also, while a top gate type TFT has been described herein as an example,the invention is applicable irrespective of the TFT structure, andapplicable to, for example, a bottom gate type (rearward stagger type)TFT and a forward stagger type TFT.

Second Embodiment

An explanation will be given below in FIG. 5A to a method (referredbelow to as color filter method), in which a white light emittingelement and a color filter are combined together.

The color filter method is a system, in which red, green, and blue lightemitting are obtained by forming a light emitting element having anorganic chemical compound presenting white light emitting and passingthe obtained white light emitting through a color filter.

There are various methods, by which white light emitting is obtained,and an explanation will be given here to the case where a light emittinglayer made of a polymeric material and being formable by coating isused. In this case, doping of a pigment on a polymeric material makingthe light emitting layer can be carried out by solution adjustment andthe layer can be extremely easily obtained as compared with a depositionmethod, in which codeposition for doping of a plurality of pigments isperformed.

Concretely, formed on an anode made of a metal having a large workfunction (Pt, Cr, W, Ni, Zn, Sn, In) is a cathode formed by laminating athin film containing a metal (li, Mg, Cs) having a small work functionand a transparent conductive film (ITO (indium oxide stannic oxidealloy), indium oxide zinc oxide alloy (In₂O₃—ZnO), zinc oxide (ZnO), orthe like) after a polyvinyl carbazole (PVK) solution doped with aluminescence center pigment (1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-bilane(DCM1),Nile red, coumarin 6, or the like) acting as a light emitting layer isapplied on a whole surface to be baked, after a poly(ethylenedioxythiophene)/poly (styrenesulfonic acid) aqueous solution(PEDOT/PSS) acting as a hole injection layer is applied on a wholesurface to be baked. In addition, PEDOT/PSS uses water as a solvent andso will not be dissolved in an organic solvent. Accordingly, when thePVK is applied thereon, there is no fear of redissolution. Also, sincethe PEDOT/PSS and the PVK are different in solvent from each other, itis preferable that the same deposition chamber is not used.

Also, while there is shown above the example, in which the organicchemical compound layer is laminated, the organic chemical compoundlayer can be made a monolayer. For example, a 1,3,4-oxadiazolederivative (PBD) of electron transport property may be dispersed inpolyvinyl carbazole (PVK) of hole transport property. Also, white lightemitting can be obtained by dispersing a 30 wt % PBD as an electrontransport agent and dispersing suitable amounts of pigments of fourkinds (TPD, coumarin 6, DCM1, Nile red).

In addition, the organic chemical compound layer is formed between ananode and a cathode, and holes injected from the anode and electronsinjected from the cathode are rejoined together in the organic chemicalcompound layer to provide for white light emitting on the organicchemical compound layer.

Also, white light emitting can be obtained as a whole by appropriatelyselecting a red light emitting organic chemical compound layer, a greenlight emitting organic chemical compound layer, and a blue lightemitting organic chemical compound layer, and overlapping them for colormixture.

The organic chemical compound layer formed in the above manner is ableto provide for white light emitting as a Whole.

White light emitting from a light emitting element can be separated andObtained as red light emitting, green light emitting, and blue lightemitting by forming a color filter provided with a color layer (R),which absorbs a light emitting except red light emitting, a color layer(G), which absorbs a light emitting except green light emitting, a colorlayer (B), which absorbs a light emitting except blue light emitting,respectively, in a direction, in which the organic chemical compoundlayer produces white light emitting. Also, in the case of an activematrix type, TFT is configured to be formed between a substrate and acolor filter.

Also, a oblique mosaic arrangement, triangular mosaic arrangement, RGBGfour pixel arrangement, or RGBW four pixel arrangement as well as asimplest stripe pattern can be used for the color layer (R, G, B).

Color layers constituting a color filter are formed making use of acolor resist made of an organic photosensitive material, in whichpigments are dispersed. In addition, white light emitting haschromaticity coordinates (x, y)=(0.34, 0.35). Color reproducibility forfull color can be adequately ensured by combining white light emittingwith a color filter.

In addition, in this case, there is no need of individually coating anorganic chemical compound layer every color of light emitting becauseall films are formed by the organic chemical compound layer, whichpresents white light emitting, even when colors of light emitting thusobtained are different from one another. Also, any circularly polarizedplate for prevention of mirror reflection is not specifically necessary.

With reference to FIG. 5B, an explanation will be given below to the CCMmethod (color conversion mediums) realized by the combination of a bluelight emitting element having an organic chemical compound layer of bluelight emitting and a color conversion layer of fluorescence.

The CCM method excites color conversion layers of fluorescence with bluelight emitting outgoing from a blue light emitting element and performscolor conversion on the respective color conversion layers. Concretely,conversion of blue to red (B→R) is performed on the color conversionlayer, conversion of blue to green (B→G) is performed on the colorconversion layer, and conversion of blue to blue (B→B) is performed onthe color conversion layer (in addition, conversion of blue to blue isunnecessary), thus obtaining red, green, and blue light emitting. Withthe CCM method, TFT is configured to be formed between a substrate and acolor conversion layer to form an organic chemical compound layer in thecase of an active matrix type.

In addition, there is no need of individually coating color conversionlayers in this case. Also, any circularly polarized plate for preventionof mirror reflection is not specifically necessary.

Also, since there is caused a problem in use of the CCM method thatcolor conversion layers are excited by outdoor daylight due tofluorescence to be lowered in contrast, contrast is preferably increasedby mounting of color filters as shown in FIG. 5C.

Also, the embodiment can be combined with the first embodiment.

Third Embodiment

FIG. 4 shows an example, in which a base insulating film is formed on asemiconductor substrate and a TFT being a kind of FET is formed on thefilm.

A N type or P type single crystal silicon substrate ((100) substrate,(110) substrate, (111) substrate, or the like), or a high puritysemiconductor substrate can be is used for a semiconductor substrate 40.Also, for example, a wafer (circular) having a diameter of 200 mm to 300mm is cut to make a rectangular substrate, and then a FET is formedthereon. Alternatively, multiple patterning may be performed, in whichthe wafer is divided into sections of a desired size after a FET and alight emitting element are formed. Also, a chemical compoundsemiconductor substrate typified by a GaAs substrate, InP substrate, GaNsubstrate for GaN system epitaxis, SiC substrate, sapphire substrate,ZnSe, or the like may be used for the semiconductor substrate 40. Also,a SOI (Si on Insulator) substrate structure may be formed by means ofthe wafer applying method and the SIMOX (separation by implanted oxygen)method. This semiconductor substrate 40 is for dispersing the heatgenerated by the light emitting element.

First, a base insulating film 41 is formed on the semiconductorsubstrate 40.

The plasma CVD method is used to form, as a first layer of the baseinsulating film 41, a silicon nitride and oxide film of 10 to 200 nm(preferably, 50 to 100 nm) deposited with SiH₄, NH₃ and N₂O as reactantgas. Here, a silicon nitride and oxide film (composition ratio ofSi=32%, O=27%, N=24%, H=17%) having a film thickness of 50 nm is formed.Subsequently, the plasma CVD method is used to form, as a second layerof the base insulating film 41, a silicon nitride and oxide film of 50to 200 nm (preferably, 100 to 150 nm) deposited with SiH₄ and N₂O asreactant gas. Here, a silicon nitride and oxide film (composition ratioof Si=32%, O=59%, N=7%, H=2%) having a film thickness of 100 nm isformed. While a two-layered structure is used as the base insulatingfilm 41 in the example, a structure maybe used, in which single or twolayers of the insulating film are laminated.

Subsequently, a semiconductor layer is formed on the insulating film. Asemiconductor layer constituting an active layer of a TFT is formed bydepositing a semiconductor film having an amorphous structure by meansof known measures (the sputtering method, LPCVD method, plasma CVDmethod, or the like) and thereafter patterning that crystalsemiconductor film, which is obtained by a known crystallizationprocessing (laser crystallization method, thermal crystallization methodmaking use of a catalyst such as nickel, or the like), into a desiredconfiguration. The semiconductor layer is formed to have a thickness of25 to 80 nm (preferably 30 to 60 nm). The crystal semiconductor film isnot limited in terms of a material but preferably fowled from silicone,silicon-germanium alloy, or the like.

Also, in the case where the crystal semiconductor film is formed bymeans of the laser crystallization method, it is possible to use pulsedoscillation type or continuous emission type excimer laser, YAG laser,and YVO₄ laser. In the case where such laser is used, it is preferableto use a method, in which laser radiation emitted from a laseroscillator is linearly collected by an optical system to be irradiatedon a semiconductor film. While conditions of crystallization areselected by an operator, they adopt the frequency of pulsed oscillationof 30 Hz and the laser energy density of 100 to 400 mJ/cm² (typically,200 to 300 mJ/cm²) when excimer laser is used. When YAG laser is used,they preferably adopt the frequency of pulsed oscillation of 1 to 10 kHzusing its second harmonic and the laser energy density of 300 to 400mJ/cm² (typically, 350 to 500 mJ/ccm²). And laser radiation linearlycollected to have a width of 100 to 1000 μm, for example, 400 μm may beirradiated over the whole substrate with the overlapping ratio of linearlaser radiation being 80 to 98%.

Subsequently, surfaces of the semiconductor layer are cleaned with anetchant, which contains hydrofluoric acid, to form a gate insulatingfilm covering the semiconductor layer. The gate insulating film isformed by means of the plasma CVD method or the sputtering method tohave a thickness of 40 to 150 nm and contain silicone. In the example,the plasma CVD method is used to form the film from a silicon nitrideand oxide film (composition ratio of Si=32%, O=59%, N=7%, H=2%) having athickness of 115 nm. Of course, the gate insulating film is not limitedto a silicon nitride and oxide film but other insulating film containingsilicone may be used in a single layer or laminated structure.

Subsequently, a gate electrode 45 is formed after surfaces of the gateinsulating film are cleaned. Subsequently, the gate insulating film issubjected to etching with the gate electrode as a mask to form a gateinsulating film 42.

Subsequently, an impurities element (B, or the like) imparting p type toa semiconductor, boron is appropriately added to form a source region 43and a drain region 44. After the addition, a heating processing,irradiation of intense light, or irradiation of laser radiation isperformed to activate the impurities element. Also, plasma damage to thegate insulating film 42 and plasma damage to an interface between thegate insulating film 42 and a semiconductor layer can be recoveredsimultaneously with activation.

In the subsequent processings, the PCVD method is used to form aninterlayer insulating film 46 a made of a silicon nitride film and asilicon nitride and oxide film, and an interlayer insulating film 46 busing a flattened insulating film composed of a photosensitive ornon-photosensitive organic material (polyimide, acrylic, polyamide,polyimideamide, resist, or benzocyclobutene) formed by the coatingmethod, or a flattened insulating film (containing a coated siliconoxide film, PSG (phosphorus adding glass, BPSG (boron and phosphorusadding glass), or the like) composed of an inorganic material, or alaminated film thereof. Subsequently, after hydrogenation, a contacthole reaching the source region or the drain region is formed.Subsequently, a source electrode (wiring) 52, insulation 49, powersupply line 47, and first electrodes (drain electrodes) 48 a to 48 d areformed to complete a TFT (p channel type TFT) in the same manner as inthe first embodiment.

The subsequent processings are the same as those as in the firstembodiment, and so it suffices to form a layer 50 containing an organicchemical compound layer and a second electrode 51 made of a conductivefilm in accordance with the first embodiment.

Also, the embodiment can be freely combined with the first embodiment orthe second embodiment.

The invention constituted in the above manner will be described infurther detail with reference to the following examples.

EXAMPLES Example 1

In this example, the procedure of formation of a light emitting elementaccording to the invention will be briefly described by way of examplewith reference to FIGS. 2 and 3.

First, a known technique is used to form a MOSFET on a semiconductorplate 30. With the use of the known technique, separation of elements isperformed by a field oxide film 31, and a doping processing is performedto form a drain region 32 or a source region 3.

Also, an interlayer insulating film 33 composed of a silicon nitridefilm and a silicon nitride and oxide film is formed by means of the PCVDmethod, and an interlayer insulating film 35 is formed by using aflattened insulating film composed of a photosensitive ornon-photosensitive organic material (polyimide, acrylic, polyamide,polyimideamide, resist, or benzocyclobutene) formed by the coatingmethod, or a flattened insulating film (containing a coated siliconoxide film, PSG (phosphorus adding glass, BPSG (boron and phosphorusadding glass), or the like) composed of an inorganic material, or alaminated film thereof.

After hydrogenation, a contact hole reaching the source region or thedrain region is formed. Subsequently, a source electrode, (wiring) andfirst electrodes (drain electrodes) are formed to complete a TFT (pchannel type TFT).

In the above processings, a MOSFET (here, only the drain region 32 isshown), interlayer insulating film 33, 35, and first electrodes 36 a to36 d are formed (FIG. 3A).

It suffices in the example that a film containing as its main componentan element selected from Ti, TiN, TiSi_(x)N_(y), Al, Ag, Ni, W, WSi_(x),WN_(X), WSi_(x)T_(y), Ta, TaN_(x), TaSi_(x)N_(y), NbN, MoN, Cr, Pt, Zn,Sn, In, or Mo, or an alloy material containing, as its main componentthe element, or a chemical compound material, or a lamination of suchfilms be used in the range of 100 nm to 1 μm for the first electrodes 36a to 36 d.

In particular, the first electrode 36 a is preferably made of amaterial, typically, titanium, which is capable of ohmic contact withsilicone, to be in the range of a film thickness of 10 to 100 nm. Also,the first electrodes 36 b is preferably made of a material (TiN, TaN,MoN, Pt, Cr, W, Ni, Zn, Sn) having a large work function in the case ofa thin film, and suffices to range in film thickness from 10 to 500 nm.Also, the first electrodes 36 c is preferably made of a light-reflectivemetallic material, typically, a metallic material containing as its maincomponent Al or Ag, and suffices to range in film thickness from 100 to600 nm. In addition, the first electrodes 36 b also functions asblocking layer for preventing alloying of the first electrodes 36 c andthe first electrode 36 a. Also, the first electrodes 36 d is preferablymade of a material, typically, metal nitride (TiN, WN, or the like), forprevention of oxidation, prevention of corrosion, or prevention ofhillock of the first electrodes 36 c, and suffices to range in filmthickness from 20 to 100 nm. In addition, the first electrodes 36 d maybe omitted.

Also, the first electrodes 36 a to 36 d can be formed simultaneouslywith other wirings, for example, a source wiring 34, power supply line,or the like.

Subsequently, an insulation (called bank, partition, barrier, or thelike) is formed to cover an end (portion contacting with the drainregion 32) of the first electrode (FIG. 3B). While an inorganic material(silicon oxide, silicon nitride, silicon oxide and nitride, or thelike), a photosensitive or non-photosensitive organic material(polyimide, acrylic, polyamide, polyimideamide, resist, orbenzocyclobutene), or a lamination of these materials, or the like canbe used to make the insulation, a photosensitive organic resin is usedin the example. For example, when a positive type photosensitive acrylicis used as a material for the insulation, a curved surface having aradius of curvature is preferably made only on an upper end of theinsulation. Also, the insulation can use both a negative type material,which is made insoluble in an etchant by photosensitive radiation, and apositive type, which is made soluble in an etchant by light.

Subsequently, the first electrodes 36 c, 36 d are partially removedwhile the insulation is subjected to etching as shown in FIG. 3C. It isessential to perform etching so that an inclined surface is formed on anexposed surface of the first electrode 36 c and an exposed surface ofthe first electrode 36 b is flattened. In the etching, dry etching orwet etching suffices to be carried out once or plural times, and acondition with a hi_(g)h ratio of selection is selected for the firstelectrode 36 b and the first electrode 36 c. And it is preferable thatan upper end of the insulation finally have a radius of curvature of 0.2μm to 3 μm. Also, finally, an angle (inclination, taper angle) of theinclined surface directed toward a center of the first electrode is inexcess of 30° but short of 70° to reflect a light emitting from a layercontaining an organic chemical compound, which is formed later.

Subsequently, a layer 38 containing an organic chemical compound isformed by means of the deposition method, or the coating method. Forexample, when the deposition method is used, deposition is carried outin a deposition chamber, in which evacuation is achieved until degree ofvacuum becomes equal to or lower than 5×10⁻³ Torr (0.665 Pa),preferably, reaches 10⁻⁴ to 10⁻⁶ Pa. At the time of deposition, theorganic chemical compound is beforehand vaporized by resistance heatingand scattered toward the substrate upon opening of a shutter at the timeof deposition. The vaporized organic chemical compound is scatteredupward to be deposited on the substrate through apertures provided on ametal mask. Lamination achieved by deposition forms a layer containingthe organic chemical compound to present white color as a whole lightemitting element.

For example, white color can be obtained by sequentially laminatingAlq₃, Alq₃, p-EtTAZ, and TPD (aromatic diamine), which are partiallydoped with Nile red, which is a red light emitting pigment.

Also, in the case where a layer containing an organic chemical compoundis formed by means of the coating method making use of spin coating,baking is preferably made by vacuum heating after coating. For example,it suffices that after a poly (ethylenedioxythiophene)/poly(styrenesulfonic acid) aqueous solution (PEDOT/PSS) acting as a holeinjection layer is applied on a whole surface to be baked, a polyvinylcarbazole (PVK) solution doped with a luminescence center pigment(1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-bilane(DCM1),Nile red, coumarin 6, or the like) acting as a light emitting layer beapplied on the whole surface to be baked.

Also, while an example, in which the organic chemical compound comprisesa lamination, has been shown, the organic chemical compound can be madea monolayer: For example, a 1,3,4-oxadiazole derivative (PBD) ofelectron transport property may be dispersed in polyvinyl carbazole(PVK) of hole transport property. Also, white light emitting can beobtained by dispersing a 30 wt % PBD as an electron transport agent anddispersing suitable amounts of pigments of four kinds (TPD, coumarin 6,DCM1, Nile red). Also, a layer made of a polymeric material and a layermade of a low molecular material may be laminated to provide the organicchemical compound. Also, the organic chemical compound layer may containan inorganic material, for example, silicone.

Subsequently, a thin conductive film (here, aluminum film) is depositedand laminated on a thin film (film formed by codeposition of an alloysuch as MgAg, MgIn, AlLi, CaF₂, CaN, or the like, or an elementbelonging to a first group or a second group in the periodic table andan aluminum) containing a metal having a small work function (FIG. 2B).The aluminum film has a high capability of blocking moisture and oxygenand is preferably suited to a conductive film 39 in improvingreliability of the light emitting device. In addition, FIG. 2B shows across section taken along the chain line A-A′ in FIG. 2(A). Thelaminated film is sufficiently thin to permit passage of light emittingand functions as a cathode in the example. Also, a transparentconductive film (ITO (indium oxide stannic oxide alloy), indium oxidezinc oxide (In₂O₃—ZnO), zinc oxide (ZnO), or the like) may be used inplace of the thin conductive film. Also, an auxiliary electrode may beprovided on the conductive film 39 in order to attain a low resistancein a cathode. Also, it suffices that at the time of formation of acathode, resistance heating in deposition is used to selectively formthe cathode with the use of a deposition mask.

The light emitting element thus obtained exhibits white light emittingin a direction indicated by an arrow in FIG. 2B, and can reflect laterallight on inclined surfaces of the first electrode 36 c to increase aquantity of light emitting in directions indicated by arrows. Inaddition, dotted lines in FIG. 2A indicate regions, in which a fieldoxide film for separation of elements, or gate wirings are formed.

After formation up to the second electrode (conductive film 39) has beenachieved in the above processings, a sealing substrate (transparentsubstrate) is stuck by a sealing agent in order to seal the lightemitting element formed on the substrate 30. In addition, a spacer madeof a resin film may be provided in order to ensure a spacing between thesealing substrate and the light emitting element. And an inert gas suchas nitrogen or the like is filled in a space inside the sealing agent.In addition, an epoxy based resin is preferably used as the sealingagent. Also, the sealing agent is desirably a material permittingpermeation of as small amount of moisture and oxygen as possible.Further, a substance (drying agent) effective in absorbing oxygen andwater may be contained inside the space.

By enclosing the light emitting element in the space in the abovemanner, it is possible to completely isolate the light emitting elementfrom outside and to prevent a substance, such as moisture and oxygen,which promotes deterioration of an organic chemical compound layer, fromentering from outside. Accordingly, it is possible to obtain a highlyreliable light emitting device.

Example 2

An explanation will be given below to an example, in which an auxiliaryelectrode is formed, with reference to FIGS. 6 and 7.

FIG. 6A is a top plan view showing pixels, and FIG. 6B is a crosssectional view taken along the chain line A-A′.

Processings for forming so far as an insulation 67 are the same as thosein the Example 1, and so are omitted here. The insulation 37 in FIG. 2Bcorresponds to the insulation 67 in FIG. 6B.

In accordance with the Example 1, a field oxide film, drain region 62,interlayer insulating films 63, 65, first electrodes 66 a to 66 d, andthe insulation 67 are formed on a substrate having an insulatingsurface.

Subsequently, a layer 68 containing an organic chemical compound isselectively formed. In the example, the layer 68 containing an organicchemical compound is selectively formed by means of the depositionmethod, in which a deposition mask is used, or the ink jet method.

Subsequently, an auxiliary electrode 60 is selectively formed on theinsulation 67 by means of the deposition method, in which a depositionmask is used. The auxiliary electrode 60 suffices to be set to have afilm thickness ranging from 0.2 μm to 0.5 μm. In the example, theauxiliary electrode 60 is shown in FIG. 6A as being arranged in aY-direction, but such arrangement is not specifically limitative but maybe such that an auxiliary electrode 70 is arranged in a X-direction asshown in FIG. 7. In addition, a cross sectional view taken along thechain line A-A′ shown, in FIG. 7 is the same as that in FIG. 2B.

Subsequently, a thin conductive film (here, aluminum film) 69 isdeposited and laminated on a thin film (film formed by codeposition ofan alloy such as MgAg, MgIn, AlLi, CaF₂, CaN, or the like, or an elementbelonging to a first group or a second group in the periodic table andan aluminum) containing a metal having a small work function, in thesame manner as in the Example 1. The laminated film is sufficiently thinto permit passage of light emitting and functions as a cathode in theexample. Also, a transparent conductive film (ITO (indium oxide stannicoxide alloy), indium oxide zinc oxide (In₂O₃—ZnO), zinc oxide (ZnO), orthe like) may be used in place of the thin conductive film. Also, in theexample, the auxiliary electrode 60 is provided on the insulation 67 ina manner to contact with the thin conductive film 69 in order to attaina low resistance in a cathode.

The light emitting element thus obtained exhibits white light emittingin a direction indicated by an arrow in FIG. 6B, and can reflect laterallight emitting on inclined surfaces of a first electrode 66 c toincrease a quantity of light emitting in directions indicated by arrows.

Also, since formation of the auxiliary electrodes 60, 70 in the examplematerializes a low resistance in a cathode, the example can be appliedto a device having a large-sized pixel section.

Also, in the example, the auxiliary electrode 60 is formed after thelayer 68 containing an organic chemical compound is formed, but suchorder of formation is not specifically limitative but the layercontaining an organic chemical compound may be formed after theauxiliary electrode 60 is formed.

Also, the example can be freely combined with any one of the first tothird embodiments and the example 1.

Example 3

An explanation will be given to this example with reference to FIGS. 9Aand 9B being a view showing an outward appearance of a whole lightemitting device of an active matrix type. In addition, FIG. 9A is a topplan view showing a light emitting device, and FIG. 9B is a crosssectional view taken along the line A-A′ in FIG. 9A. The referencenumeral 901 denotes a source signal conductor driving circuit indicatedby dotted lines, 902 a pixel section, and 903 a gate signal conductordriving circuit. Also, the reference numeral 904 denotes a sealedsubstrate, and 905 a sealing agent, an interior surrounded by thesealing agent 905 defining a space 907. Also, the reference numerals 930a, 930 b denote IC chips mounted on a semiconductor substrate 910 bymeans of the COG (chip on glass) method, wire bonding method, or the TAB(tape automated bonding) method.

While FIG. 9A shows mounting of IC chips provided with a memory, CPU,D/A converter, or the like, the invention uses a semiconductor substrateas a substrate, so that it is possible to form a complex integratedcircuit (memory, CPU, D/A converter, or the like) on the same substrate.FIG. 8 is a system block diagram of a semiconductor device in the formof a portable type information terminal such as PDA, in which variouscircuits are fabricated on a semiconductor substrate.

A circuit mounted on a semiconductor device shown in FIG. 8 comprises apower source circuit composed of a stabilized power source and an op-ampof high speed and high accuracy, controller, memory, correction circuit,or the like. Further, a CPU can be fabricated on the same substrate, andinformation processed in the CPU is output as an image signal a datasignal to a controller from an image signal processing circuit. Thecontroller functions to convert an image signal and clock intorespective timing specifications of a data signal side driving circuitand a gate signal side driving circuit.

Concretely, the controller functions to divide a image signal into datato corresponding to respective pixels in a display and to convert ahorizontal synchronizing signal and a vertical synchronizing signal,which are input from outside, into a start signal for the drivingcircuits and a timing control signal for ac conversion of an internalpower circuit.

It is demanded for portable type information terminals such as PDA to beusable outdoors and in the train for a long time with a chargeable typebattery as a power source without being connected to an AC receptacle.Also, it is simultaneously demanded for such electronic device to bemade lightweight and small in size with importance being attached toeasiness in carrying. Being increased in capacity, a battery having amajor part of a weight of an electronic device will be increased inweight. Accordingly, in order to decrease power consumption of such anelectronic device, there is a need of taking measures in the softwareaspect, such as control on time, in which a backlight is put on, andsetting of a standby mode.

For example, when no input signal is input into a CPU, a standby modecomes out to synchronously suspend a part of operations. In the pixelsection, EL elements are damped in light emitting intensity, ordisplaying of a picture itself is stopped. Alternatively, measures aretaken such that memory elements are fabricated in respective pixels andswitching to a mode of displaying a still picture is made. In thismanner, it is possible to decrease power consumption of the electronicdevice.

Also, in order to display a still picture, reduction in powerconsumption can be achieved by suspending the functions of an imagesignal processing circuit of a CPU, VRAM, and so on.

In addition, the reference numeral 908 denotes a wiring for transmissionof a signal input into the source signal line driving circuit 901 andthe gate signal line driving circuit 903, through which wiring a videosignal and a clock signal are received from a FPC (flexible printcircuit) being an external input terminal. In addition, while only theEPC is shown, a printed wire board (PWB) may be mounted to the FPC. In,the specification of the present application, the light emitting deviceincludes not only a light emitting device itself but also a lightemitting device in a state, in which a FPC or a PWB is mounted thereon.

Subsequently, an explanation will be given to a cross-sectionalstructure with reference to FIG. 9B. A driving circuit and a pixelsection are formed on the semiconductor substrate 910, and here thesource signal conductor driving circuit 901 as a driving circuit and thepixel section 902 are shown.

In addition, the source signal conductor driving circuit 901 comprises aCMOS circuit, in which an n-channel type FET 923 and a p-channel typeFET 924 are combined together. Also, TFTs composing the driving circuitmay be formed by a known CMOS circuit, PMOS circuit, or a NMOS circuit.Also, while the example presents a driver integrated type, in which adriving circuit is formed on a substrate, the driving circuit is notnecessarily required to be formed on the substrate, but can be formedoutside the substrate.

Also, the pixel section 902 is formed by a plurality of pixels includinga switching FET 911, a current control FET 912, and a first electrode(anode) 913 electrically connected to a drain of the FET.

Also, insulations 914 are formed on both ends of the first electrode(anode) 913, and the first electrode partially comprises inclinedsurfaces along sides of the insulations 914. The inclined surfaces ofthe first electrode are formed simultaneously with formation of theinsulations 914. The inclined surfaces reflect a light, emitted from alayer 915 containing an organic chemical compound, to increase aquantity of luminescence in directions indicated by an arrow in FIG. 9.

Also, the layer 915 containing an organic chemical compound isselectively fowled on the first electrode (anode) 913. Further, a secondelectrode (cathode) 916 is formed on the layer 915 containing an organicchemical compound. Thereby, a light emitting element 918 composed of thefirst electrode (anode) 913, the layer 915 containing an organicchemical compound, and the second electrode (cathode) 916 is formed.Here, since the light emitting element 918 is white light emitting inthe example, a color filter (here, an overcoat layer is not shown forthe sake of simplicity) composed of a color layer 931 and a BM 932 isprovided.

Also, a third electrode (auxiliary electrode) 917 constituting a part ofthe configuration shown in the Example 2 is formed on the insulations914 to materialize a to decrease in resistance of the second electrode.Also the second electrode (cathode) 916 also functions as a wiringcommon to all pixels to be connected electrically to a FPG 909 via thethird electrode 917 and the connection wiring 908.

Also, in order to seal the light emitting element 918 formed on thesemiconductor substrate 910, the sealing agent 905 is used forattachment of the sealing substrate 904. In addition, a spacer made of aresin film may be provided in order to ensure a spacing between thesealing substrate 904 and the light emitting element 918. And an inertgas such as nitrogen or the like is filled in a space 907 inside thesealing agent 905. In addition, an epoxy based resin is preferably usedas the sealing agent 905. Also, the sealing agent 905 is desirably amaterial permitting permeation of as small moisture and oxygen aspossible. Further, a substance effective in absorbing oxygen and watermay be contained inside the space 907.

Also, it is possible in the example to use, in addition to a glasssubstrate and a quartz substrate, a plastic substrate made of FRP(Fiberglass-Reinforced Plastics), PVF (polyvinylfluoride), myler,polyester, acrylic, or the like, as a material that constitutes thesealing substrate 904. Also, after the sealing agent 905 is used foradhesion of the sealing substrate 904, sealing with the sealing agentcan be made so as to cover sides (exposed surfaces).

By enclosing the light emitting element in the space 907 in the abovemanner, it is possible to completely isolate the light emitting elementfrom outside and to prevent a substance, such as moisture and oxygen,which promotes deterioration of an organic chemical compound layer, fromentering from outside. Accordingly, it is possible to obtain a highlyreliable light emitting device.

Also, the example can be freely combined with any one of the first tothird embodiments, the example 1 and the example 2.

Example 4

By embodying the invention, all electronic equipments are completed,which incorporate a module (active matrix type EL module) having a lightemitting element.

Such electronic equipments include a video camera, digital camera,head-mount display (goggle type display), car navigation, car stereo,personal computer, portable information terminal (mobile computer,portable telephone, or electronic book or the like). FIGS. 10A to 10F,11A, and 11B show example of such electronic equipments.

FIG. 10A shows a personal computer including a body 2001, image inputunit 2002, display unit 2003, a keyboard 2004, and so on. However, theinvention uses a semiconductor substrate (for example, a wafer having adiameter of 300 mm), and so screen sizes are small or medium.

FIG. 10B shows a video camera including a body 2101, display unit 2102,sound input unit 2103, control switches 2104, battery 2105, an imagereceiving 2106, and so on.

FIG. 10C shows a mobile computer including a body 2201, camera unit2202, image receiving unit 2203, control switch 2202, a display unit2303, and so on.

FIG. 10D shows a goggle type display including a body 2301, display unit2302, arms 2203, and so on.

FIG. 10E shows a player making use of a recording medium (referred belowto as recording medium), in which programs are recorded, and including abody 2401, display unit 2402, speaker unit 2403, recording medium 2404,control switches 2405, and so on. In addition, the player enablesappreciation of music, appreciation of movie, games, and Internet withthe use of DVD (Digital Versatile Disc), CD, or the like as a recordingmedium.

FIG. 10F shows a digital camera including a body 2501, display unit2502, eyepiece unit 2503, control switches 2504, image receiving unit(not shown), and so on.

FIG. 11A shows a portable telephone including a body 2901, sound outputunit 2902, sound input unit 2903, display unit 2904, control switches2905, antenna 2906, image input unit (CCD, image sensor, or the like)2907.

FIG. 11B shows a portable book (electronic book) including a body 3001,display units 3002, 3003, recording medium 3004, control switches 3005,an antenna 3006, and so on.

As described above, the invention is applied to a very wide range ofapplications and applicable to methods of fabricating electronicequipments in all fields. Also, the electronic equipments in the examplecan be also materialized with the use of configurations of anycombinations of the first to third embodiments and the Examples 1 to 3.

According to the invention, a light emitting in a lateral direction(direction parallel to a substrate surface) among a light emitted from alayer containing an organic chemical compound is reflected by inclinedsurfaces, which are formed on stepped portions of a first electrode,whereby a total quantity of luminescence taken out in a certaindirection (direction passing through the second electrode) can beincreased. That is, it is possible to materialize a light emittingelement involving less loss, such as stray light, in luminescence.

Also, according to the invention, heat generated when a light emittingelement is driven is dissipated through a semiconductor substrate, andso it is possible to materialize a light emitting element of highreliability.

Also, various circuits in addition to the light emitting element can beintegrated on a semiconductor substrate to achieve a greatminiaturization of a semiconductor device.

What is claimed is:
 1. (canceled)
 2. A display device comprising: asingle crystal semiconductor substrate; a pixel portion comprising aplurality of pixels; wherein each of the plurality of pixels comprises:a transistor comprising a channel formation region; a first insulatinglayer over the transistor; a first electrode over the first insulatinglayer; a second insulating layer covering a peripheral portion of thefirst electrode; a layer comprising an organic material over the firstelectrode and the second insulating layer; and a second electrode overthe layer comprising the organic material, wherein a source or a drainof the transistor is electrically connected to the first electrode,wherein a thickness of the first electrode in a region covered by thesecond insulating layer is larger than a thickness of the firstelectrode in a region exposed from the second insulating layer, whereinthe channel formation region is in the single crystal semiconductorsubstrate, wherein the channel formation region is surrounded by anelement separation film which is on the single crystal semiconductorsubstrate, and wherein the first electrode overlaps the elementseparation film.
 3. The display device according to claim 2, furthercomprising a nitride insulating film over and in contact with theelement separation film and a gate electrode of the transistor.
 4. Thedisplay device according to claim 2, wherein the element separation filmis an oxide film formed by oxidation of part of the single crystalsemiconductor substrate.
 5. The display device according to claim 2,wherein the element separation film is an oxide film embedded in atrench in the single crystal semiconductor substrate.
 6. The displaydevice according to claim 2, wherein the first electrode has a stackedstructure of a layer containing titanium and a layer containingaluminum.
 7. The display device according to claim 2, wherein the layercomprising the organic material is capable of emitting white light. 8.The display device according to claim 7, further comprising: alight-transmitting substrate over the second electrode and a coloredlayer on the light-transmitting substrate.
 9. The display deviceaccording to claim 2, further comprising: a driver circuit of the pixelportion; a controller circuit; and a D/A converter, wherein the drivercircuit, the controller circuit and the D/A converter are fabricated onthe single crystal semiconductor substrate.
 10. A display modulecomprising the display device according to claim 2 and a FPC bonded tothe single crystal semiconductor substrate.
 11. An electronic equipmentcomprising the display module according to claim 10, wherein theelectronic equipment is one selected from the group consisting of avideo camera, a digital camera, a head-mount display, a car navigation,a DVD player, an electronic game equipment, a portable informationterminal and a personal computer.
 12. A display device comprising: asingle crystal semiconductor substrate; a pixel portion comprising aplurality of pixels; wherein each of the plurality of pixels comprises:a transistor comprising a channel formation region; a first insulatinglayer over the transistor; a first electrode over the first insulatinglayer and having a depression portion; a second insulating layercovering the first electrode except the depression portion; a layercomprising an organic material over the first electrode and the secondinsulating layer; and a second electrode over the layer comprising theorganic material, wherein the first electrode has a stacked structure ofa layer containing titanium and a layer containing aluminum, wherein thelayer containing aluminum is in contact with the layer comprising theorganic material in the depression portion, wherein a source or a drainof the transistor is electrically connected to the first electrode,wherein the channel formation region is in the single crystalsemiconductor substrate, wherein the channel formation region issurrounded by an element separation film which is on the single crystalsemiconductor substrate, and wherein the first electrode overlaps theelement separation film.
 13. The display device according to claim 12,further comprising a nitride insulating film over and in contact withthe element separation film and a gate electrode of the transistor. 14.The display device according to claim 12, wherein the element separationfilm is an oxide film formed by oxidation of part of the single crystalsemiconductor substrate.
 15. The display device according to claim 12,wherein the element separation film is an oxide film embedded in atrench in the single crystal semiconductor substrate.
 16. The displaydevice according to claim 12, wherein the layer comprising the organicmaterial is capable of emitting white light.
 17. The display deviceaccording to claim 16, further comprising a light-transmitting substrateover the second electrode and a colored layer on the light-transmittingsubstrate.
 18. The display device according to claim 12, furthercomprising: a driver circuit of the pixel portion; a controller circuit;and a D/A converter, wherein the driver circuit, the controller circuitand the D/A converter are fabricated on the single crystal semiconductorsubstrate.
 19. A display module comprising the display device accordingto claim 12 and a FPC bonded to the single crystal semiconductorsubstrate.
 20. An electronic equipment comprising the display moduleaccording to claim 19, wherein the electronic equipment is one selectedfrom the group consisting of a video camera, a digital camera, ahead-mount display, a car navigation, a DVD player, an electronic gameequipment, a portable information terminal and a personal computer. 21.A display device comprising: a single crystal semiconductor substrate; apixel portion comprising a plurality of pixels; wherein each of theplurality of pixels comprises: a first transistor comprising a firstchannel formation region; a second transistor comprising a secondchannel formation region; a first insulating layer over the firsttransistor and the second transistor; a first electrode over the firstinsulating layer; a second insulating layer covering a peripheralportion of the first electrode; a layer comprising an organic materialover the first electrode and the second insulating layer; and a secondelectrode over the layer comprising the organic material, wherein athickness of the first electrode in a region covered by the secondinsulating layer is larger than a thickness of the first electrode in aregion exposed from the second insulating layer, wherein a source or adrain of the first transistor is electrically connected to a gate of thesecond transistor, wherein a source or a drain of the second transistoris electrically connected to the first electrode, wherein an elementseparation film is provided between the first channel formation regionand the second channel formation region, and wherein the first electrodeoverlaps the element separation film.
 22. The display device accordingto claim 21, further comprising a nitride insulating film over and incontact with the element separation film and a gate electrode of each ofthe first transistor and the second transistor.
 23. The display deviceaccording to claim 21, wherein the element separation film is an oxidefilm formed by oxidation of part of the single crystal semiconductorsubstrate.
 24. The display device according to claim 21, wherein theelement separation film is an oxide film embedded in a trench in thesingle crystal semiconductor substrate.
 25. The display device accordingto claim 21, wherein the first electrode has a stacked structure of alayer containing titanium and a layer containing aluminum.
 26. Thedisplay device according to claim 21, wherein the layer comprising theorganic material is capable of emitting white light.
 27. The displaydevice according to claim 26, further comprising a light-transmittingsubstrate over the second electrode and a colored layer on thelight-transmitting substrate.
 28. The display device according to claim21, further comprising: a driver circuit of the pixel portion; acontroller circuit; and a D/A converter, wherein the driver circuit, thecontroller circuit and the D/A converter are fabricated on the singlecrystal semiconductor substrate.
 29. A display module comprising thedisplay device according to claim 21 and a FPC bonded to the singlecrystal semiconductor substrate.
 30. An electronic equipment comprisingthe display module according to claim 29, wherein the electronicequipment is one selected from the group consisting of a video camera, adigital camera, a head-mount display, a car navigation, a DVD player, anelectronic game equipment, a portable information terminal and apersonal computer.